/**
 * Provide effect for line
 * @module echarts/chart/helper/EffectLine
 */
define(function (require) {

    var graphic = require('../../util/graphic');
    var Line = require('./Line');
    var zrUtil = require('zrender/core/util');
    var symbolUtil = require('../../util/symbol');
    var vec2 = require('zrender/core/vector');

    var curveUtil = require('zrender/core/curve');

    /**
     * @constructor
     * @extends {module:zrender/graphic/Group}
     * @alias {module:echarts/chart/helper/Line}
     */
    function EffectLine(lineData, idx, seriesScope) {
        graphic.Group.call(this);

        this.add(this.createLine(lineData, idx, seriesScope));

        this._updateEffectSymbol(lineData, idx);
    }

    var effectLineProto = EffectLine.prototype;

    effectLineProto.createLine = function (lineData, idx, seriesScope) {
        return new Line(lineData, idx, seriesScope);
    };

    effectLineProto._updateEffectSymbol = function (lineData, idx) {
        var itemModel = lineData.getItemModel(idx);
        var effectModel = itemModel.getModel('effect');
        var size = effectModel.get('symbolSize');
        var symbolType = effectModel.get('symbol');
        if (!zrUtil.isArray(size)) {
            size = [size, size];
        }
        var color = effectModel.get('color') || lineData.getItemVisual(idx, 'color');
        var symbol = this.childAt(1);

        if (this._symbolType !== symbolType) {
            // Remove previous
            this.remove(symbol);

            symbol = symbolUtil.createSymbol(
                symbolType, -0.5, -0.5, 1, 1, color
            );
            symbol.z2 = 100;
            symbol.culling = true;

            this.add(symbol);
        }

        // Symbol may be removed if loop is false
        if (!symbol) {
            return;
        }

        // Shadow color is same with color in default
        symbol.setStyle('shadowColor', color);
        symbol.setStyle(effectModel.getItemStyle(['color']));

        symbol.attr('scale', size);

        symbol.setColor(color);
        symbol.attr('scale', size);

        this._symbolType = symbolType;

        this._updateEffectAnimation(lineData, effectModel, idx);
    };

    effectLineProto._updateEffectAnimation = function (lineData, effectModel, idx) {

        var symbol = this.childAt(1);
        if (!symbol) {
            return;
        }

        var self = this;

        var points = lineData.getItemLayout(idx);

        var period = effectModel.get('period') * 1000;
        var loop = effectModel.get('loop');
        var constantSpeed = effectModel.get('constantSpeed');
        var delayExpr = zrUtil.retrieve(effectModel.get('delay'), function (idx) {
            return idx / lineData.count() * period / 3;
        });
        var isDelayFunc = typeof delayExpr === 'function';

        // Ignore when updating
        symbol.ignore = true;

        this.updateAnimationPoints(symbol, points);

        if (constantSpeed > 0) {
            period = this.getLineLength(symbol) / constantSpeed * 1000;
        }

        if (period !== this._period || loop !== this._loop) {

            symbol.stopAnimation();

            var delay = delayExpr;
            if (isDelayFunc) {
                delay = delayExpr(idx);
            }
            if (symbol.__t > 0) {
                delay = -period * symbol.__t;
            }
            symbol.__t = 0;
            var animator = symbol.animate('', loop)
                .when(period, {
                    __t: 1
                })
                .delay(delay)
                .during(function () {
                    self.updateSymbolPosition(symbol);
                });
            if (!loop) {
                animator.done(function () {
                    self.remove(symbol);
                });
            }
            animator.start();
        }

        this._period = period;
        this._loop = loop;
    };

    effectLineProto.getLineLength = function (symbol) {
        // Not so accurate
        return (vec2.dist(symbol.__p1, symbol.__cp1)
            + vec2.dist(symbol.__cp1, symbol.__p2));
    };

    effectLineProto.updateAnimationPoints = function (symbol, points) {
        symbol.__p1 = points[0];
        symbol.__p2 = points[1];
        symbol.__cp1 = points[2] || [
            (points[0][0] + points[1][0]) / 2,
            (points[0][1] + points[1][1]) / 2
        ];
    };

    effectLineProto.updateData = function (lineData, idx, seriesScope) {
        this.childAt(0).updateData(lineData, idx, seriesScope);
        this._updateEffectSymbol(lineData, idx);
    };

    effectLineProto.updateSymbolPosition = function (symbol) {
        var p1 = symbol.__p1;
        var p2 = symbol.__p2;
        var cp1 = symbol.__cp1;
        var t = symbol.__t;
        var pos = symbol.position;
        var quadraticAt = curveUtil.quadraticAt;
        var quadraticDerivativeAt = curveUtil.quadraticDerivativeAt;
        pos[0] = quadraticAt(p1[0], cp1[0], p2[0], t);
        pos[1] = quadraticAt(p1[1], cp1[1], p2[1], t);

        // Tangent
        var tx = quadraticDerivativeAt(p1[0], cp1[0], p2[0], t);
        var ty = quadraticDerivativeAt(p1[1], cp1[1], p2[1], t);

        symbol.rotation = -Math.atan2(ty, tx) - Math.PI / 2;

        symbol.ignore = false;
    };


    effectLineProto.updateLayout = function (lineData, idx) {
        this.childAt(0).updateLayout(lineData, idx);

        var effectModel = lineData.getItemModel(idx).getModel('effect');
        this._updateEffectAnimation(lineData, effectModel, idx);
    };

    zrUtil.inherits(EffectLine, graphic.Group);

    return EffectLine;
});